bnx2x: Correct memory preparation and release

Since commit 15192a8cf there have been a memory leak upon rmmod
of the bnx2x driver.

This corrects the memory leak and corrects the zeroing of internal
memories upon driver load.

Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>